There is some degree of uncertainty in seepage field with the influence of spatial variability of hydraulic parameters. The characteristic of KL(Karhunen-Loeve) expansion of random field is analyzed and the principle of KLME method for stochastic analysis of seepage field is presented. It is found that the KLME method has a good computational efficiency because of taking advantage of mean square convergence of KL expansion and asymptotic convergence of perturbation expansion, and transforming the random partial differential equation to a set of recursive deterministic partial differential equations. The stochastic simulation of unsaturated flow is conducted, and the uncorrelated, perfectly positive correlated and negative correlated three cases between parameters of unsaturated hydraulic function are studied. The study result shows that mutual-correlation between hydraulic parameters has large effect on statistics of seepage field.